title: Fibre type-specific satellite cell content in two models of muscle disease.
abstract: OBJECTIVE
  Muscle satellite cells (SCs) are responsible for the regenerative events following muscle fibre injury. This study aimed to improve our understanding of SC behaviour in two models of muscle disorder with different pathological mechanisms and onset of disease.
  
  
  RESULTS
  Pax7(+) SC content was assessed in types I and II fibres of patients with Duchenne muscular dystrophy (DMD; n = 9; age 13 ± 2 years), polymyositis/dermatomyositis (PM/DM; n = 9; age 52 ± 12 years) and in controls (n = 5; age 26 ± 5 years). Pax7(+) SCs number in type I and II fibres was higher (P < 0.05) in DMD and in PM/DM compared to controls. Type I fibres were associated with a higher number of Pax7(+) SCs compared to type II fibres only in DMD; Pax7(+) SCs number in type I fibres was about threefold higher in DMD compared to PM/DM (P < 0.05). In DMD, Pax7(+) SC content in small regenerating fibres (0.09 ± 0.09 SCs/fibre) was similar to that in fibres from healthy skeletal muscle. The proportion of activated SCs (Ki-67(+) SCs) was fivefold lower in DMD (0.4 ± 0.4%) compared to PM/DM (2.8 ± 2%). Pax7(+) cells located outside the basal lamina were observed in DMD muscles only.
  
  
  CONCLUSIONS
  The capacity to generate new SCs is increased even in severely impaired muscles and a fibre type-specific enhancement of SC occurs in type I muscle fibres in DMD.
authors.affiliation: Muscle and Exercise Physiology Research Group (MEP-RG), School of Health and Medical Sciences, Örebro University, Örebro, Sweden; Laboratory of Exercise Physiology (LPE EA 4338), University of Lyon, Saint-Étienne, France; Unit of Myology, University Hospital of Saint-Etienne, Saint-Étienne, France.
authors.forename: Landry-Cyrille
authors.initials: LC
authors.lastname: Bankolé
authors.forename: Léonard
authors.initials: L
authors.lastname: Feasson
authors.forename: Elodie
authors.initials: E
authors.lastname: Ponsot
authors.forename: Fawzi
authors.initials: F
authors.lastname: Kadi
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002452:Cell Count; D002648:Child; D003882:Dermatomyositis / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism / Q000473:pathology; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism / Q000473:pathology; D020388:Muscular Dystrophy, Duchenne / Q000378:metabolism / Q000473:pathology*; D051763:PAX7 Transcription Factor / Q000378:metabolism; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism / Q000473:pathology*; D055815:Young Adult
chemical_list: D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human
keywords: Duchenne muscular dystrophy; Pax7; polymyositis and dermatomyositis; regeneration